Process of partial saponification of cellulose ester material and product thereof



' Patented Oct. 25, 1932 ,No Drawing.

UNITED STATES PATENT OFFICE CAMILLE DREYFUS, OF NEW YORK, N. Y.,

AND HERBERT IPLAI'T, OF CUMBERLAND,

MARYLAND, ASSIGNQRS TO CELANESE CORPORATION OF AMERICA, A CORPORA- TION OF DELAWARE PROCESS OF PARTIAL SAPONIFICA'IION F CELLULOSE ESTER MATERIAL AND PRODUCT THEREOF .faces of the fibres thereof only. Other objects of our invention Will appear from the following detailed description. Heretofore it has been proposed to saponify organic ester of cellulose material in 3 order to alter its dyeing properties. However the prior processes of saponification saponified or tended to saponify the fibres throughout the whole mass thereof, so that the safe ironing point would not be raised unless the organic ester material were completely or heavily saponified. Moreover by. the former processes, the organic ester material would dye unevenly.

We have found that if textile materials containing organic esters of cellulose are treated with a limited quantity of an alkaline solution, and the same is quickly heated, in-

tense saponification on the surface of the fibres of a material takes place, whereby the safe ironing point is raised and the textile material may dye evenly.

In accordance with our treatment we treat textile materials containing organic esters of cellulose by padding or otherwise applying a limited quantity of a solution of alkaline material and then quickly drying the so treated material.

The textile material to be treated may be in the form of yarns but is preferably in the form of a fabric containing yarns of the organic ester of cellulose. Any suitable organic ester of cellulose may be employed such as cellulose acetate, cellulose formats, cellulose propionate and cellulose butyrate. The fabrics need not consist wholly of yarns of organic esters of cellulose but may also be a mixed fabric containing yarns of organic esters of cellulose and also yarns of other material. Examples of such mixed fabrics are mixed cellulose acetate and cotton, mixed Application filed September 1, 1923. v Serial No. 303,600.

do not produce the desired result. The alkaline solution employed may be of any suitable concentration and may be applied in such quantities that an amount of alkali equivalent to 3 to 12 and preferably 3 to 7% of caustic soda based on the weight of the organic ester remains on the textile material. Usually the quantity of solution applied is to 100% by weight of the organic ester of cellulose material. Therefore if say, an amount of solution equal to 50% of the weight of the textile material is to be applied, and it is desired that the textile material retain 6% of its weight of caustic soda, then a caustic soda solution of 12% concentration will be applied.

After the alkaline solution has been padded on the fabric, the fabric isthen immediately dried in a quick manner. A convenient method is to pass the fabric around rotating heated drums or cans. Another method is to place the fabric in a heated atmosphere. Generally, temperatures of C. to C. will be employed for drying the fabric.

After this treatment, the fabric may then be dyed or submitted to any desired process. However it is important that the textile ma terial should be thoroughly washed to remove all traces of sodium or potassium acetate that is formed during the saponification process before such material is used, since we have found that the presence of such acetate lowered the temperature at which the fabric scorches.

The fabric treated by our invention is made of fibres of cellulose esters which is intensely saponified on the surface of the fibres. By this is meant that only the outer skin or layer of the fibre is saponified to substantially completely reconstituted cellulose, while the interior of the fibre consists of practically unaffected organic ester of cellulose. This is indicated by the fact that if a textile material comprisi'ng yarns of acetone soluble cellulose acetate is treated by our invention so that it suffers a loss of weight of say 6% by the saponification, the resultant product is almost completely soluble in acetone, whereas a cellulose acetate of corresponding acetylvalue which is not saponified on the surface is not soluble in acetone. Moreover if textile materials containing organic esters of cellulose are treated by other methods of saponification such as treatment with gaseous ammonia or alcoholic solutions of caustic soda whereby the interior of the fibres is also saponified, such material must be saponified to such an extent as to lose or 60% of its acidyl value before its safe ironing point is raised appreciably. On the other hand by our method we produce fibres containing organic esters of cellulose which have been saponified only 3 to 7% or more, as measured y the loss of weight during the saponification, which fabric has a safe ironing point that is raised or C. or more. Thus when a cellulose acetate fabric having a safe ironing point of 220 C. is treated by our process, its safe ironing point is raised to 260 (3., 290 C. or more.

Fabrics when partially saponified by our process, apart from the enormous aconomic advantage of our new processes, wet out in a much shorter time than do untreated fabrics of organic ester of cellulose, which is a further great advantage in dyeing, washing and other processes. Moreover they may be dyed very easily and without creases, while untreated fabrics require a longer time to dye,

and special machinery or special care must be employed for dyeing the untreated fabric to avoid creases. The fabric when treated by our invention dyes very uniformly and level, and may be dyed with dyes that have an afiinity for either organic esters of cellulose or for cotton. Organic ester of cellulose fabric when saponified in the old manner produces uneven dyeing.

If desired, thickening agents such as gum arabic, gum tragacanth, British gum, etc., may be added to the alkaline solution that is padded onto the organic ester of cellulose material.

In order further to illustrate our invention the following specific example is given by way of illustration without limiting the scope thereof.

Example is arranged so that the fabric picks up :n amount of caustic soda solution equal to its own weight.

The fabric is then passed immediately over and around rotating drums or cans that are heated to about 70 C. until the fabric is dry. When heavier fabrics are treated, it is advisable to cover the first drum or can with cotton cloth to prevent sticking. The fabric may then be immediately dyed or'printed, after which it is thoroughly washed to remove the last traces of sodium acetate. The fabric so treated has a high safe ironing point usually above 270 C. and has been saponified to the extent of about 5 loss of weight. It will be seen that this process is rapid, simple and extremely economical.

It is to be understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made therein without departing from the spirit of our invention.

Having described our invention what we claim and desire to secure by Letters Patent 1. Method of treating textile materials containing organic esters of cellulose comprising applying thereto a limited quantity of an aqueous alkaline saponifying agent and immediately and quickly drying the same.

2. Method of treating textile materials containing cellulose acetate applying thereto a limited quantity of an aqueous alkaline saponifying agent and immediately and quickly drying the same.

3. Method of increasing the safe ironing point of a fabric containing an organic ester of cellulose comprising padding thereon an aqueous alkaline saponifying agent in such amount as to contain alkali corresponding to 3 to 12 per cent of caustic soda based on the wei ht of the fabric and immediately and quic ly drying the same.

4. Method of increasing the safe ironing point of a fabric containing cellulose acetate comprising padding thereon an aqueous alkaline sapomfying agent in such amount as to contain alkali corresponding to 3 to 12 per cent of caustic soda based on the weight of the fabric and immediately and quickly drying the same.

5. Method of treating fabrics containing yarns of organic esters of cellulose comprising padding an aqueous alkaline saponifying agent onto such fabric in such manner that alkali in amounts equivalent to 3 to 12 per cent of caustic soda based on the weight of the fabric is applied to the fabric, immediately drying the fabric on heated surfaces and then thoroughly washing said fabric, whereby the safe ironing oint of the fabric is materially increased an the yarns thereof are intensely saponified on the surface.

6. Method of treating fabrics containing yarns of cellulose acetate comprising padding an aqueous alkaline saponifying agent onto such fabric in such manner that alkali in amounts equivalent to 3 to 12 per cent of caustic soda based on the weight of the fabricis applied to the fabric, immediately drying the fabric on heated surfaces and then thoroughly washing said fabric, whereby the safe ironing point of the fabric is materially increasedand the yarns thereof are intensely saponified on the surface.

7. Method of treating textile materials containing organic esters of cellulose comprising applying thereto a limited quantity of an aqueous alkaline saponifying agent and immediately and quickly drying the same on heated surfaces.

8. Method of treating textile materials containing cellulose acetate comprising applying thereto a limited quantity of an aqueous alkaline saponifying agent and immediately and quickly drying the same on heated surfaces.

In testimony whereof, we have hereunto subscribed our names.

-CAMILLE DREYFUS.

HERBERT PLATT. 

